Safety device for rotary motors



Feb. 26, 1952 INVENTOR BVxILLIAM R.MACLAY.

ms ATTORNEY.

Patented Feb. 26, 1952 UNITED STATES ''PAT'E'N'T .OFFICE SAFETY DEVICE FOR'ROTARY MOTORS Willam.R.".Maclay, Athens, Pa.,..assignoi' toxIngersoll-Rand .'Company,.New York, N. Y.,a cor- .v poration offNew Jersey Application November 16, 1949," Serial No."127,668

4. Claims. i 1

l'This invention relates toy governors, fand more Vparticularly to safety devices for-rotary -motors.

This invention -is particularly adaptable.to

pneumatically operated-tools suchas `surface grinders, and operates to shut down the grinder in theA event of'overspeed-of the driving vmotor Inasmuch as surface grinders are normally de- `signed to `dofwork= at high speed, an extremely :dangerous conditionis encountered inl-the event -the speed governorffails to operate. That is, due to` this high speedfrof the grinder when loaded. the grinder can,` under the unloaded condition, :reach a. speed, if thesspeed governor-fails to operate. atwhich `the'grinding wheel willbe. .thrown z:apart due to centrifugal force.

Z'It is accordinglyone object of this invention to permanently shutdown the motorrin thefevent zithespeed. governor' fails to operate.

Another object -is.to provide; aasavfety .device '.:zthatis simple'in design and compact inzconstruction.

Further obj ectsI will become apparent from the i following specification and accompanying.: drawt'ings inwhich,

Figure 1 is a-longitudinal vertical elevation of fa surface `grinder provided with a safetydevice constructed in accordance with the practice of l, the invention,

Figure 2 is a top view of a speed; governor and an OVelSlleed` governor,

FigureV 3 .is a transverse view taken through .A Figure-1 along theline 3-3 looking inthe direc- ,.tion of the arrows,

Figure 4 isa sideelevation of the speed governorand overspeed governor, and

. Figure 5 is a transverse viewtaken through Figure 4` along the line 5--5 looking in the direction of the arrows.

VRefering to the drawings, the sped control governorand the overspeed govenor, indicated in their entirety by I0, are shown adapted to a contain the. speedA of thev motor relatively constant by controlling .the supplyv of the .power to the .-.fmotor1l2- In furtherance, to ,this end, movement As -a result of this' 1 2 of fly-weights I3'. of .this governor is .transmitted througha pin I4 tomovea valve .l5v forcontrolling the supply of power to .the motor I2.

If, for any reason, the speed control governor fails to operate, fly-weights I6. of. theoverspeed governor will release springs I'I Which,;.on'their release, move v.the pin I4..to close-.thefvalve I5 whenever the speedof the'` motor I2reaches some predetermined: maximum value. r With. `this-sarrangment. then, aV means .,is" provided for .con-

. trolling Athe speed' of the grinder I l. and `in...the

event of faulty operatiorrof .the speedgovernor. the overspeed governor. comeszinto' action ,to shut down .the motor beforeit: reaches somepredetermined speed.

Referring in Ygreater detail tov the. construction of the grinder, the motor I2includes a-.rotorf I8 in which are slidablyimounted vanes Igienclosed ina cylindricalhousing 20. Airinlet anddis- Acharge ports 2| -and 22, respectively, are,pro

vided in the housing 20, and end plates.:23,.en

closev the opposite endsofthe housing 20. The

motor I2 is suitably housed in thelower portion (as viewed inFigure. 1) of a casing 24'having a handle 28 integral therewith; andV bolted tothe lowei` end iof the casing. is a shieldj 25,. for a grinding wheel 26 secureditothe motor .spindle 2'I. The upper end Yportion of the rotor I8: vextends through theplate Y2i! intoxtheigovernor chamber I ldened, by.,aqcylindric`al` member,` 29 press-.tted within the. upperi portionfof. thefcasing 241and is journaled .insa bearing 43ILprovided on the .upperplate 23.

Thek boreof the upper portionofzthe member 29 is somewhat reduced in diameter and serves to dene a valve. chamber H5 for the valve I5. In furtherance to this'end,` thereis tted within the lreduced bore' a Acup-shaped bushing 13I` forithe reception for the similarly shaped valve I5. Movement of the valve I5 vvto controll the'r supply of power ltothe motor I2.is facilitated ifby .the meansof a1 pin III. which extends. through"l.the bottom of the element 3l' andbears lagainst'the bottom of the valve I5. Thus, Vlongitudinal movementY of the piny I4 is .transmitted-Ito the valve I5 to control the'ow of `compressedffair through a passage32`to the motor I2.

'The Dassage'-32 is divided into 1 sections-32 and 32b by the chamber II5; the Vsection 32.` extends upstream of the chamber through. the member 29, casing 24 and the handle 28.in which v is provideda manually operable valve 50 for controlling the ow ofk air through this-section 32a. The section 32b extends downstream of the chamber II5 .throughrthe bushing 3l, member 29 and casing 24 to the inlet port 2 I, thus air flowing through the passage 32 to the motor must pass through the valve chamber wherein the flow of pressure fluid is controlled by valve I5. In furtherance to this end, the downstream end of the passage 32 terminates in the valve chamber I I5 on one side (the upper as viewed in Figure 1) of a valve stop, the ring 33 in the bushing 3 I, and the upstream end of the passage, or section, 32b terminates in the valve chamber II5 on the opposite side of the ring 33. Thus, movement of the valve I5 in the upward direction (as viewed in Figure 1) serves to reduce the flow of compressed air through the passage 32; and when the movement of the valve in this direction is halted by the ring 33, the lip, or upper edge, of the valve I5 is held in a sealing relation against the ring `3.3-which for this purpose is made of rubberand the end of the passage 32b is completely covered by the valve I5 so that the supply of pressure fluid to the motor I2 is cut-olf.

Movement of the pin I4 for actuating the valve I5 to regulate the speed of the motor I2 is attained by means f the speed governor comprising a pair of fly-weights I3 pivoted between a pair of parallel plates 34 mounted vertically on a horizontal plate 35 having a stem 3S threaded in the rotor I8. The fly-weights I3 are, in -their preferred form, U-shaped and the lower legs thereof are pivoted on pins 31 which pass perpendicularly through the vertical plates 34 at the opposite end portions thereof. Extending inwardly from and integral with the lower legs of the fly-weights I3 are levers 33 the free ends of which underlie a head 38 on a rod 40 slidable in the stem 36 and extending into a. recess, or central bore, 4I in the rotor I8. Threaded on the end of the rod 4I) within the recess is a nut 42 which serves as a stop for one end of a spring 43, the other end of which bears against the end of the stem 35.

The spring 43 biased in this fashion, tends to hold the rod 40 in its lower limiting position and the head 39 at all times in contact with the levers 38. The length of the pin I4 is chosen such that when the rod 43 is in its lowermost position, the pin I4, the lower end of which rests on the head 39, permits the valve I5 to assume a position whereat the upper edge of the valve I5 lies in or slightly below a horizontal plane through the lowermost point of the end of the section. 32b registering with the chamber II5. Thus slight upward movement of the pin I4 will cause the valve I5 to throttle the flow of pressure fluid to the motor I2.

With this arrangement, whenever the speed of the motor I2 reaches some predetermined value, the fly-weights I3 will swing outwardly movingr the free ends of the levers 38 upwardly to lift the head 33 and move the pin I4 to actuate the valve I5 to throttle the iiow of compressed air through the section 32b thereby preventing overspeedingl of the motor I2. Whenever the speed of the motor falls to a value whereat the centrifugal force acting on the fly-weights I3 is not suicient to overcome the force exerted on the rod 40 in the opposite direction by the spring 43, the rod 40 will be returned, by the spring 43, toward its lower limiting position thereby'permitting the valve I5 to increase the ow of pressure fluid to the motor I2.

In the event of faulty operation of the speed governor, such that overspeeding of the motor I2 occurs, a situation that would arise in the event the fly-weights I3 stuck with the rod 40 in its lower limiting position, the overspeed governor comes into action to shut down the motor permanently-that is, the operator will be unable to start the motor I2 without dismantling the grinder. general, a pair of fly-weights I6 movable on a plane perpendicular to the plane of movement to the weights I3, or in other words, movable in a horizontal plane (as viewed in Figure 1), and which releasably engage springs I1 adapted, when released, to move the valve I5 into the closed position.

In furtherance to this end, a pair of wings 44 arranged in a diametrical fashion with respect to the axis, or rotor IB, of the motor I2, project outwardly from the plates 34. The ily-weights I6 are pivoted at their ends on pins 45 extending through the wings 44; and in the other end portions of the ily-weights I6 are holes 46 through which are hooked the ends of helical springs 41. The springs 41 extend perpendicularly through the plates 34-holes |34 are provided in the plates 34 to permit this arrangement-and are pinned at their other ends to the most distant plate 35.

Arranged in this fashion, the springs 41 tend to hold projections 5I, on the free ends of the weights I6, against the sides of the vertical plates 34 to prevent the release of the springs I1 arranged outside of the plates 34 and having their hooked ends engaged by the projections 5I. The springs I1, formed from a resilient wire, extend in bowed fashion over the weights I6 and parallel to and alongside the Vertical plates 34, and curl about the head ends of the pins 31 and the ends are turned into holes 48 provided in the side of the wings 44 to limit the movement of springs on the pins 31. The opposite, or hooked, end portion 52 of each of these springs I1 are L- shaped with the vertical legfof the L extending downwardly, as viewed in Figure 4, so that the projection 5I lies within the angle formed by said portion 52 of the spring I1. In other Words, the spring I1 extends above the weight I6 lalong l substantially its entire length, then turns downwardly parallel and adjacent to the inner edge of the projection 5I, and then the extreme end of said portion 52 is turned under and bears against the lower surface of the projection 5I adjacent the free end thereof. With this arrangement, slight movement of the projection 5I away from the plate 34 will release the spring I1; that is, the resistance of the spring I1 to sidewise movement will overcome the tendency of the spring to swing out with the weight I6, and the projection will move clear of the hooked end of the spring I1,

In order to limit the outward movement of the weights I8, and thereby preclude stretching the spring 41 beyond its elastic limit and also to prevent the weights I5 from swinging out and striking the wall of the member 29, a stop is provided to halt such movement after the projection 5I releases the spring I1. Specifically this stop comprises a pin 53 press-fitted in the weight I6 and extending radially from the lower surface thereof into a hole 54 formed in the wing 44. The location and size of the hole 54 is such that the degree of arc through which the projection 5I may travel before the pin 53 strikes the outer edge surface of the hole 54 and halts the outward movement of the weight I6, will assure that the spring I1 will be released before the weight I5 reaches this outer limiting position.

The springs I1 are arranged so that when The overspeed governor comprises in' they are engaged by the fly-weights I6, they are in a compressed state'and in the released position they move upwardly to actuate the pin I4 to close the valve I5. Thus, whenever the flyweights I6 swing outwardly, with respect to the head 39, the projections 5I move clear of the hooked ends of the springs I'I thereby releasing the springs I'I and the bowed portions thereof tend to straighten and hence move upwardly (as viewed in Figure 1) to actuate the pin I4. In furtherance t this end, a circular plate 49 lying in a plane perpendicular to the movement of the springs I'I is adapted to the lower end portion of the pin I4, thus a large surface area is presented against which the springs II strike upon release by the weights IE5. It is also to be noted, that in order to eliminate the possibility of the springs II striking the plate 49 and then slippingr clear, the marginal portion of the plate 49 is turned downwardly, as viewed in Figure 4, and that the springs I1, by virtue of their construction, make contact with the plate near the center thereof. (See Fig. 4.)

Reviewing briey the operation of the grinder provided with a preferred form of the safety device, compressed air is supplied to the motor I2 through the passage 32 by turning the manually operated valve 50 in the handle 28 into the open position. Compressed air passes from the passage 32 through the inlet port 2| and expands A;

in the motor I2 thereby rotating the vanes I9 and thence is exh-austed from the motor I2 through the ports 22 to the atmosphere.

With the valve 50 in full open position the speed of the motor I2 is maintained at a relative constant value by the action of the speed governor. Specifically, when the speed of the motor-and hence the rotary speed, in a horizontal plane, of the y-weights I3 and I6- reaches some predetermined value, the yweights I3 are moved outwardly under the influence of centrifugal force thereby lifting the rod 40 which movement is transmitted through the pin I4 to the valve I5 thereby diminishing the supply of pressure fluid to the motor I2.

In the event of faulty operation of the speed governor, when the motor I2 reaches some predetermined speed-this speed being somewhat higher than the value at which the y-weights I3 are moved outwardly-the y-Weights I6 will be swung outwardly by centrifugal force thereby releasing the springsY I'I which snap upwardly (as viewed in Figure 1) striking the plate 49 and moving the valve I5 into the closed position to shut down the motor I2. In order to reset the springs II it is necessary to dismantle the grinder and manually hook the ends of thev springs I1 over the free ends of the y-weights. Accordingly, it is impossible for the operator to purposely or inadvertently operate the grinder with a faulty speed governor without rst dismantling the tool, at which time the speed governor may be repaired.

In view of the foregoing disclosure it becomes apparent that a safety device constructed in accordance with the practice of the invention accompilshes among others the object hereinbefore stated. It is further to be noted thatl such a. safety device is not only simple in construction 6 and, therefore, less likely to fall into disrepar', but it is also extremely compact in its arrangement of parts and, therefore, readily adaptable to a great variety of rotary tools without materially increasing their bulk.

While I have shown and described a specific form of my invention it is to be understood that various changes and modifications may be made without departing from the spirit of the invention as set forth in the appended claims.

I claim:

1. A safety device for a rotary motor, comprising a valve for controlling the flow of power to the motor, a governor for controlling the speed of said motor by actuating said valve to control the flow of power to the motor, a spring arranged to act in the released position to close said valve, and a speed responsive element releasably engaging said spring to place the spring under stress and acting at a predetermined speed of said motor to release said spring.

2. A safety device for a motor, comprising a valve for controlling the supply of power to the motor, a mounting on the axis of said motor and rotatable therewith, two sets of y-Weights on said mounting, a pin for transmitting the movement of one set of y-weights to actuate said valve for governing the speed of the motor, and a resilient member under stress releasably engaged by the other set of fly-weights and arranged to act in its released position to actuate said pin for shutting down the motor.

3. A safety device for rotary motors, comprising a valve for controlling the supply of power to the motor, a set of fly-weights moving in response to the speed of the motor for actuating said valve, a resilient member arranged to move said valve into the closed position, and a second set of y-weights releasably engaging said member to place the member under stress against such movement and movable in a plane perpendicular to the plane of movement of the rst said weights to release said member at a predetermined speed of the motor.

4. A safety device for a rotary tool having a housing with a uid actuated motor at one end thereof, comprising a reciprocating valve in the other end of the housing, a mounting on the axis of said motor between the valve and the motor, a governor on the mountingv for actuating said valve to control the speed of the motor, a resilient member on said mounting and adapted to move said valve into the closed position, and an element on said mounting releasably engaging said member to prevent closing of the valve thereby and movable in response to a predetermined speed of the motor to release said member to permit closing of the valve.

WILLIAM R. MACLAY.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,213,791 Bailey Jan. 23, 1917 2,422,733 Jimerson June 24. 1947 

